U.S. patent application number 10/918963 was filed with the patent office on 2005-04-14 for method and apparatus for destruction of liquid toxic wastes and generation of a reducing gas.
This patent application is currently assigned to HYLSA, S.A. DE C.V.. Invention is credited to Villarreal-Trevino, Juan Antonio, Viramontes-Brown, Ricardo.
Application Number | 20050079127 10/918963 |
Document ID | / |
Family ID | 34198070 |
Filed Date | 2005-04-14 |
United States Patent
Application |
20050079127 |
Kind Code |
A1 |
Viramontes-Brown, Ricardo ;
et al. |
April 14, 2005 |
Method and apparatus for destruction of liquid toxic wastes and
generation of a reducing gas
Abstract
The invention relates to a method and system for destroying
liquid toxic materials for example polychlorinated biphenyls, and
producing a reducing gas. In a preferred embodiment, harmful
intermediates are not generated when the toxic materials are
destroyed due to the reducing atmosphere produced by partial
combustion with a molecular-oxygen-containing gas and steam. Liquid
materials containing high concentrations of PCB's are mixed with
non-toxic hydrocarbons for sustaining an autothermic reaction. The
efficiency of the PCB's destruction process exceeds the required
environmental regulations and produces a useful reducing gas which
can be utilized as a synthesis gas in chemical processes or as a
fuel for heat and/or power production.
Inventors: |
Viramontes-Brown, Ricardo;
(San Pedro Garza Garcia, MX) ; Villarreal-Trevino, Juan
Antonio; (Guadalupe, MX) |
Correspondence
Address: |
FROMMER LAWRENCE & HAUG
745 FIFTH AVENUE- 10TH FL.
NEW YORK
NY
10151
US
|
Assignee: |
HYLSA, S.A. DE C.V.
Nuevo Leon
MX
|
Family ID: |
34198070 |
Appl. No.: |
10/918963 |
Filed: |
August 16, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60495924 |
Aug 18, 2003 |
|
|
|
Current U.S.
Class: |
423/650 ;
422/600 |
Current CPC
Class: |
C10K 1/12 20130101; C01B
2203/1211 20130101; C10J 2300/0946 20130101; C10J 2300/0973
20130101; C01B 3/32 20130101; A62D 2101/28 20130101; C10J 3/723
20130101; C01B 3/36 20130101; C10K 1/101 20130101; Y02P 30/20
20151101; C10J 3/485 20130101; C01B 2203/0255 20130101; A62D
2101/22 20130101; C10J 2300/093 20130101; A62D 2101/04 20130101;
C10J 2300/1838 20130101; A62D 3/38 20130101; C10J 2300/1884
20130101; C10J 2300/1892 20130101 |
Class at
Publication: |
423/650 ;
422/194 |
International
Class: |
C01B 003/24; B01J
010/00 |
Claims
What is claimed is:
1. A method for the destruction of a toxic material comprised in a
liquid hydrocarbon without producing harmful intermediates,
comprising the steps of: mixing said liquid hydrocarbon comprising
said toxic material with steam and a molecular oxygen-containing
gas in a flow channel and regulating the flow rates of said liquid
hydrocarbon and said steam and oxygen gases so that a velocity of
the mixture of liquid and gas at the outlet of said flow channel is
above about 40 m/s, introducing said mixture of liquid and gas in a
reaction vessel having a refractory lining at a temperature above
about 650.degree. C., maintaining said producing high-temperature
gases comprising molecular hydrogen within said reaction vessel at
least about 2 seconds; maintaining a temperature at the outlet of
said reaction vessel above about 1000.degree. C.; and cooling and
washing said gaseous products with water, wherein a reducing gas is
produced comprising hydrogen and carbon monoxide substantially free
of said toxic material as a result of the partial combustion of
said liquid hydrocarbon.
2. The method according to claim 1, wherein said toxic material is
comprised of one or more polychlorinated biphenyls, pesticides,
chlorofluorocarbons, halogenated benzenes, halogenated phenols,
halogenated alkanes, halogenated cycloalkanes, halogenated dioxins
or halogenated dibenzofurans or combinations thereof.
3. The method according to claim 1, wherein said liquid hydrocarbon
is oil.
4. The method according to claim 1, wherein said velocity of the
mixture of liquid and gas at the outlet of said flow channel is
above about 50 m/s.
5. The method according to claim 1, wherein the refractory lining
of said reaction vessel is maintained at a temperature above about
750.degree. C.
6. The method according to claim 2, wherein said liquid hydrocarbon
contains less than about 50% by weight of polychlorinated
biphenyls.
7. The method according to claim 2, wherein said liquid hydrocarbon
containing polychlorinated biphenyls is mixed with hydrocarbons not
containing polychlorinated biphenyls before introducing said
contaminated hydrocarbon in said reaction vessel, in order to
secure the autothermic partial combustion of the mixture of
hydrocarbons.
8. The method according to claim 6, wherein said mixture of
hydrocarbons has less than about 50% by weight of polychlorinated
biphenyls before being introduced into said reaction vessel.
9. The method according to claim 7, wherein said mixture of
hydrocarbons has less than about 10% by weight of polychlorinated
biphenyls before being introduced into said reaction vessel.
10. The method according to claim 1, wherein the water used for
said gas cooling is mixed with an alkaline compound for
neutralizing the acidity derived from chlorine absorption by said
water.
11. The method according to claim 1, wherein the water used for
said gas cooling is treated for concentrating and recuperating HCl
derived from chlorine absorption by said water.
12. A system for the destruction of liquids comprising toxic
materials and producing a reducing gas comprising hydrogen and
carbon monoxide, said system comprising: a partial combustion
chamber, said combustion chamber having a refractory lining adapted
to being heated and maintained at high temperature whereby flame
gases are produced, and said chamber having an inlet and an outlet;
a flow channel having a length to diameter ratio of at least about
4, and where a stream of oxygen, a stream of steam and a stream of
liquid comprising said toxic materials are intimately mixed; said
flow channel being in communication with said combustion chamber
inlet, and gas cooling means communicating with said combustion
chamber outlet for quenching said flame gases.
13. A system according to claim 12, wherein the length to diameter
ratio of said flow channel is at least about 30.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the handling and disposal
of toxic wastes. More particularly, the present invention relates
to transforming toxic waste materials, such as
halogenated-organic-compounds having liquids and solids, to a
non-toxic reducing gas. The non-toxic reducing gas can be utilized
as a synthesis gas, as a fuel or as a chemical reducing agent in,
for example, the chemical reduction of iron oxides into metallic
iron.
[0002] Documents cited in this text, and all documents cited or
referenced in the documents cited in this text, are incorporated
herein by reference. Documents incorporated by reference into this
text or any teachings therein may be used in the practice of this
invention. Documents incorporated by reference into this text are
not admitted to be prior art. Furthermore, authors or inventors on
documents incorporated by reference into this text are not to be
considered to be "another" or "others" as to the present inventive
entity and vice versa, especially where one or more authors or
inventors on documents incorporated by reference into this text are
an inventor or inventors named in the present inventive entity.
BACKGROUND OF THE INVENTION
[0003] Hazardous and environmentally damaging substances, such as
polychlorinated biphenyls (PCB's), and their safe destruction are a
major concern in the industrialized world. PCB's are one of the
best known compounds referred to in the industry as POP's
(persistent organic pollutants). Such pollutants also include waste
pesticides such as DDT, and CFC's (chlorofluorocarbons),
halogenated benzenes, halogenated phenols, halogenated alkanes,
halogenated cycloalkanes, halogenated dioxins and halogenated
dibenzofurans.
[0004] A number of methods for disposing of and destroying waste
toxic materials have been proposed. See for example a report titled
"Destruction Technologies for Polychlorinated Biphenyls (PCBs)" by
M. S. M. Muheebur Rahuman, Luigi Pistone, Ferruccio Trifiro and
Stanislav Miertus (2002) (incorporated herein by reference). Some
of the methods described in this report can be summarized as
follows: (1) high temperature incineration with oxygen; (2)
incineration in cement kilns; (3) super critical oxidation; (4)
electrochemical oxidation; (5) solvated electron technology; (6)
chemical reduction reaction; (7) dehalogenation processes, and
other complex technologies.
[0005] Incineration with oxygen is typically performed in rotary
kilns at temperatures of about 870.degree. C. to 1200.degree. C.
Destruction efficiencies up to 99.9999% can be achieved. Liquid
wastes with PCB concentrations above 50 ppm are incinerated in some
places if such incineration complies with a residence time of at
least of 2 seconds at 1200.degree. C. and 3% excess oxygen in the
stack gases.
[0006] One of the problems associated with the incineration is
atmospheric oxygen control in order to prevent formation of dioxins
and benzofurans which are also toxic. Treatment of wastes in cement
kilns also involves some kind of incineration. Since they operate
at temperatures above 1400.degree. C. and the conditions therein
are highly alkaline, cement kilns decompose chlorinated organic
wastes. The quantity of waste is, however, limited to a small
fraction of the fuel requirements of the kiln and no liquid or
solid residues are generated since all residues come out of the
kiln bound to the product. When operated properly, destruction of
chlorinated compounds can be 99.00% complete without affecting the
quality of the exhaust gas. Not all cement kilns, however, meet the
required conditions for this use and not all companies are willing
to handle waste products in their normal cement production
operations.
[0007] Chemical reduction technologies involve the gas-phase
chemical reduction of organic compounds with hydrogen at
temperatures above about 850.degree. C. This process has been
applied for destruction of a variety of organic compounds such as
chlorophenols, dioxins, chlorobenzenes, pesticides, herbicides and
insecticides. These compounds are converted to methane. About 40%
of the methane produced is then converted to hydrogen and CO
through the water gas shift reaction, and the remaining methane is
converted to hydrogen in a catalytic steam reformer which is
combined with the waste oil so that the oxidation reaction takes
place in a reducing atmosphere devoid of oxygen. In this way the
possibility of dioxin and furan formation is said to be
eliminated.
[0008] U.S. Pat. No. 3,140,155 to J. A. Cull et al. relates to a
process and furnace for hydrogen chloride recovery from chlorinated
residues such as hexachloro-cyclopentadiene, and trichlorobenzenes.
Although Cull's process involves the reaction of chlorinated
compounds with air/oxygen and steam, the gases produced from such
reaction are not intended to comprise significant proportions of
hydrogen and CO but only to obtain as much hydrogen chloride as
possible.
[0009] U.S. Pat. No. 3,305,309 to R. G. Woodland et al. relates to
a process and apparatus for converting halogenated organic
materials into gaseous products comprising carbon dioxide and
hydrogen halide. The halogenated organic compounds are reacted with
air or oxygen and steam in a tubular burner wherein an intimate
mixture of steam and the halogenated organic material is effected
by passing the steam under pressure through a restricted zone into
an expanded zone. The halogenated material is introduced into the
expanded zone and brought into contact with the steam. The mixture
is then atomized by passing it through a constricted zone into an
expanded zone where the mixture is combined with oxygen or air.
Preferably the atomized mixture is enveloped in the gaseous medium
as it is injected into the combustion zone.
[0010] U.S. Pat. Nos. 4,074,981 and 4,468,376 relate to processes
for disposing of a halogenated organic material by partial
oxidation of said organic material together with a
hydrocarbonaceous material and a nitrogen compound with a free
oxygen-containing gas. The partial oxidation produces a synthesis
gas containing hydrogen, carbon monoxide, carbon dioxide, hydrogen
cyanide, hydrogen halide and ammonia. The synthesis gas produced is
contacted with water containing additional ammonia in order to
neutralize the hydrogen halide.
[0011] U.S. Pat. No. 4,631,183 to Lalancette et al. relates to a
process for the destruction of toxic organic halogenated substances
comprising treating in a reaction chamber under a reductive
atmosphere and at high temperatures in the range from 1000.degree.
C. to 1600.degree. C. a mixture of a toxic halogenated substance,
carbon and a carbonate or bicarbonate of an alkali metal whereby
the vapors of the alkali metal are generated in situ to cause total
degradation of the toxic substance into non-toxic components.
Carbon monoxide is formed during the process and it is oxidized to
carbon dioxide in a separate combustion chamber. The resulting
gases from this process are fully oxidized, but a useful gas
comprising hydrogen and carbon monoxide is not produced.
[0012] DE 41 09 231 A1 relates to a process for transforming waste
halogenated hydrocarbons to produce a gas containing hydrogen and
carbon monoxide by partial oxidation with oxygen in a flame
reaction. The hydrocarbon is combined with oxygen under pressure.
The gases produced are cooled down and thereafter are passed
through a catalytic converter to transform the gases into a desired
final composition through the well-known water gas shift reaction.
The hot gases are quenched with water having an alkaline additive.
The process of this patent, however, presents a number of
drawbacks, e.g. the halogenated hydrocarbon is reacted with oxygen
only without a temperature moderator as steam, therefore, the flame
temperature is extremely high requiring a very specialized
refractory lining. The carbon dioxide content in the gases produced
by partial oxidation is relatively high, requiring an additional
reactor to convert a portion of that carbon monoxide to hydrogen.
The water needed for such water-shift reaction is added by
evaporation of the quenching water. This method of supplying the
water is not efficient because it depends on the saturation
conditions of the gases.
[0013] U.S. Pat. No. 4,402,274 relates to a partial oxidation of
the toxic material followed by quenching of the reaction
products.
[0014] U.S. Pat. No. 4,140,066 to Rathjen et al. relates to a
process for the thermal decomposition of polychlorinated organic
compounds such as polychlorinated phenyls and biphenyls comprising
heat treating said compounds in a flame, in a high-turbulence
combustion chamber in a pulsating spiral flow at a temperature of
at least about 850.degree. C. with a residence time of at least 0.1
seconds in the presence of an excess of at least about 5% by weight
of oxygen based on the carbon to be burnt, the PCB being present in
the fuel feed in about 0.1 to 30% by weight. The process of this
patent is a full combustion process and does not produce a reducing
gas as a result of the oxidation reaction.
[0015] U.S. Pat. Nos. 4,819,571 and 5,050,511 to Hallet relate to a
system for the destruction of organic waste material (PCB's and
related waste organic matter) which comprises subjecting the waste
material to reduction with hydrogen at a temperature above
600.degree. C. with indirect heating of the reduction chamber, and
thereafter oxidizing the hot resultant reaction mixture at a
temperature above 1000.degree. C. The system includes a reduction
vessel and an adjacent combustor for the oxidation reaction. The
process of this patent comprises a two-stage method requiring at
least two high-temperature reactors and a hydrogen generator.
[0016] U.S. Pat. Nos. 5,449,854 and 5,609,104 to Yap relate to a
method and an incinerator for incinerating halogenated organic
compounds. The process comprises two steps, one wherein an
auxiliary fuel, for example natural gas, is partially combusted to
generate hydrogen and a second step wherein the gases produced in
the first step are fully combusted with additional oxygen. This
two-step process purportedly minimizes formation of halogenated
furans and dioxins. The process of Yap is complex and is intended
to incinerate the halogenated compounds, not to produce a useful
gas.
[0017] U.S. Pat. No. 4,851,600, British patent 1,350,727 and German
patent DE 41 25 518 also relate to processes for destruction of
halogenated organic materials wherein said materials are fully
combusted in multiple combustion steps or in the presence of metals
for capturing chlorine.
[0018] U.S. Pat. Nos. 4,869,731, 5,074,890 and 4,950,309 relate to
a process for the thermal decomposition of toxic refractory organic
substances. Toxic substances are contacted with an oxidizing medium
and steam at a temperature in the range of 2500.degree. F.
(1371.degree. C.) to 3200.degree. F. (1760.degree. C.) for a period
of 5 to 500 milliseconds in a reaction chamber. The process of this
patent requires extremely high temperatures and the reaction time
is very short. Therefore, the materials are also contacted with
incandescent carbon or refractory.
[0019] U.S. Patent Publication No. 2002/0098133 A1 relates to
processes for the conversion of halogenated materials to one or
more useful products. These products can be a useful acid and/or a
product synthesis gas.
[0020] U.S. Pat. Nos. 2,928,460, 3,462,250, 3,545,926, 3,743,606
and 3,874,592 relate to burners for partial oxidation of
hydrocarbons. These patents purportedly provide for designs for
achieving atomization of the liquid hydrocarbons by impinging a
gaseous stream of an oxidant with a separate stream of the
hydrocarbon at the tip of the burner. These burner designs,
however, rely more on the atomization of the liquid rather than
favoring a dispersed flow pattern of the liquid and gas phases, and
present the disadvantage of not producing an efficient
non-dispersed coherent flame.
[0021] Large amounts of contaminated materials, such as those
containing PCBs, and other toxic wastes are currently stored at
high cost in many places all over the world pending destruction.
This poses grave environmental risks. The prior art methods of
destroying contaminated materials, however, have a number of
drawbacks. For example, the processes in the art do not completely
destroy the PCB's. Further, the cost of operation is high;
typically without any off-setting economic benefit and the use of
complex and costly equipment and multi-step reactions are required.
Additionally, harmful intermediates can be produced.
[0022] Thus, a need exists in the art for the destruction of the
toxic materials by partial oxidation and generation of a reducing
gas in a single reaction vessel. A need also exists in the art for
an efficient and low-cost method of destroying such toxic materials
without producing harmful or unwanted intermediates.
OBJECTS AND SUMMARY OF THE INVENTION
[0023] Therefore an object of the invention can be to provide an
efficient and low-cost process and equipment for destruction of
toxic waste materials.
[0024] It is another object of the invention to provide a method
and apparatus for producing a reducing gas which can be utilized as
fuel or chemical reducing agent for example in the reduction of
iron oxides.
[0025] It is yet another object of the invention to destroy toxic
wastes, such as PCB's, without producing harmful intermediates,
such as dioxins.
[0026] Other objects will be pointed out hereinafter or will become
evident for those readers expert in the art.
[0027] In accordance with one embodiment of the present invention,
therefore, a method is provided for the destruction of a toxic
material without producing harmful intermediates, having the steps
of destroying said toxic material in a partial oxidation reaction
in a heated reaction vessel by contacting a liquid hydrocarbon
material comprised of said toxic material with steam and an
oxygen-containing source, and producing a reducing gas thereby
comprised of hydrogen and carbon monoxide.
[0028] In accordance with another embodiment of the present
invention, a system is provided for the destruction of toxic waste
materials and producing a reducing gas comprising hydrogen and
carbon monoxide, the system having a partial combustion chamber; a
burner where a stream of oxygen, steam and said toxic materials are
reacted producing high-temperature flame gases within said partial
combustion chamber; and gas cooling means for quenching said flame
gases.
[0029] In this disclosure, "comprises," "comprising" and the like
can have the meaning ascribed to them in U.S. Patent Law and can
mean, "includes," "including" and the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] In this specification and the accompanying drawings, some
preferred embodiments of the invention are shown and described, and
various alternatives and modifications thereof have been suggested.
It is to be understood that these are not intended to be exhaustive
and that many other changes and modifications can be made within
the scope of the invention.
[0031] The suggestions herein are selected and included for
purposes of illustration in order that others skilled in the art
will more fully understand the invention and the principles thereof
and will thus be enabled to modify it in a variety of forms, each
as may be best suited to the conditions of a particular use.
[0032] In the following detailed description, reference will be
made to the accompanying drawings, wherein:
[0033] FIG. 1 is a schematic diagram of the process for processing
the toxic waste hydrocarbons.
[0034] FIG. 2 is a schematic diagram of the burner utilized for
partially combusting the toxic waste hydrocarbons.
DETAILED DESCRIPTION OF ILLUSTRATIVE PREFERRED EMBODIMENTS OF THE
INVENTION
[0035] Typically, destruction of toxic wastes follows a process
whereby harmful intermediates are produced. The present invention
advantageously destroys toxic materials, such as PCB's, without
producing harmful intermediates, such as dioxins and furanes.
[0036] For example, it has hereby been unexpectedly discovered that
by making the temperature of the refractory higher than that of the
incoming materials, the efficiency of the partial combustion
reaction is increased. Further, by limiting the oxygen feed to less
than the stoichiometric amount for full combustion, toxic
intermediates are not generated. Instead, one of the end products
of the present invention is HCl, which can easily be neutralized
with NaOH. Typically, the refractory is maintained at a temperature
above about 650.degree. C., preferably at above about 750.degree.
C., depending on the type of material being gasified. Further, by
heating the refractory, fuel is saved. Indeed, the art uses extra
fuel to maintain the flame of the refractory, which the present
invention avoids.
[0037] The instant invention by, for example, using steam as the
reducing source, by regulating the oxygen ratio and by monitoring
temperature, achieves a 99.9999% efficiency in reducing toxic
wastes. Further, use of steam is cheaper than using typical
hydrocarbon fuels, and the steam can be a byproduct of a
concurrent, separate reaction.
[0038] In a preferred embodiment, the present invention carries out
the combustion reaction by mixing steam and oxygen, which mixture
envelopes a jet of PCB containing liquid in a pipe with such
dimensions as to meet the conditions for achieving a disperse
two-phase flow of within said pipe, by controlling the velocity of
the fluids in said pipe so that a controlled, narrow, coherent and
stable flame is produced within a combustion chamber surrounding
the tip of said pipe.
[0039] The present invention can be applied to virtually any
hydrocarbon and any organic contaminant including, but not limited
to, PCB's, dioxins, pesticides and solvents at any concentration.
Typical hydrocarbons include PCB-contaminated oil of electrical
equipment, pesticide wastes and other waste oils and hydrocarbons
from the petrochemical industry. The present invention also avoids
the need of a catalytic converter typically used in generating a
process gas from hydrocarbons.
[0040] The present invention provides for, for example, a method
for the destruction of a toxic material comprised in a liquid
hydrocarbon without producing harmful intermediates. The steps of
the method include mixing said liquid hydrocarbon comprising said
toxic material with steam and a molecular oxygen-containing gas in
a flow channel and regulating the flow rates of said liquid
hydrocarbon and said steam and oxygen gases so that a velocity of
the mixture of liquid and gas at the outlet of said flow channel is
above about 40 m/s, introducing said mixture of liquid and gas in a
reaction vessel having a refractory lining at a temperature above
about 650.degree. C., maintaining said producing high-temperature
gases comprising molecular hydrogen within said reaction vessel at
least about 2 seconds; maintaining a temperature at the outlet of
said reaction vessel above about 1000.degree. C.; and cooling and
washing said gaseous products with water. As a result of the
method, a reducing gas is produced comprising hydrogen and carbon
monoxide substantially free of said toxic material as a result of
the partial combustion of said liquid hydrocarbon. The toxic
material is comprised of one or more of the substances:
polychlorinated biphenyls, pesticides, chlorofluorocarbons,
halogenated benzenes, halogenated phenols, halogenated alkanes,
halogenated cycloalkanes, halogenated dioxins or halogenated
dibenzofurans or combinations thereof. In a preferred embodiment,
the liquid hydrocarbon is oil.
[0041] Preferably, the velocity of the mixture of liquid and gas at
the outlet of said flow channel is above about 50 m/s. Further, the
refractory lining of said reaction vessel is preferably maintained
at a temperature above about 750.degree. C. The liquid hydrocarbon,
in turn, preferably contains less than about 50% by weight of
polychlorinated biphenyls.
[0042] In one embodiment, the liquid hydrocarbon containing
polychlorinated biphenyls is mixed with hydrocarbons not containing
polychlorinated biphenyls before introducing said contaminated
hydrocarbon in said reaction vessel, in order to secure the
autothermic partial combustion of the mixture of hydrocarbons.
Preferably, the mixture of hydrocarbons has less than about 50% by
weight of polychlorinated biphenyls before being introduced into
said reaction vessel.
[0043] The mixture of hydrocarbons may have less than about 10% by
weight of polychlorinated biphenyls before being introduced into
said reaction vessel. Further, the water used for said gas cooling
is typically mixed with an alkaline compound for neutralizing the
acidity derived from chlorine absorption by said water. Further
still, the water used for said gas cooling is preferably treated
for concentrating and recuperating HCl derived from chlorine
absorption by said water.
[0044] The present invention also provides for a system for the
destruction of liquids comprising toxic materials and producing a
reducing gas comprising hydrogen and carbon monoxide. In a
preferred embodiment, the system includes a partial combustion
chamber, said combustion chamber having a refractory lining adapted
to being heated and maintained at high temperature whereby flame
gases are produced, and said chamber having an inlet and an outlet;
a flow channel having a length to diameter ratio of at least about
4, and where a stream of oxygen, a stream of steam and a stream of
liquid comprising said toxic materials are intimately mixed; said
flow channel being in communication with said combustion chamber
inlet; and gas cooling means communicating with said combustion
chamber outlet for quenching said flame gases. Preferably, the
length to diameter ratio of said flow channel is at least about
30.
[0045] A preferred embodiment of the invention is herein described
with reference to FIG. 1, wherein numeral 10 generally designates a
partial combustion reactor comprising a burner 12 and a refractory
lined wall 14. A stream of liquid hydrocarbon waste 16 is combined
in said burner with an oxygen-containing gas 18, which can be pure
oxygen, air or oxygen-enriched air in various proportions,
depending on the desired quality of the product gas. Steam 20
supplied from a suitable source 23, or optionally produced in
boiler 32 and fed through pipe 21, is injected to the burner 12 so
that the hydrocarbon 16, oxygen 18 and steam 20 react and produce a
high temperature flame 22 within the reaction space 24 of reactor
10. Reaction space 24 is designed according to the feeding rate of
reactants so that a residence time of the flame gases exceeds about
2 seconds, preferably about 3 seconds, at a temperature higher than
about 1600.degree. C. The high temperature flame reaction destroys
the complex molecules of the halogenated compounds, under a
reducing atmosphere. The oxygen-containing gas is fed to burner 12
in an amount less than the amount stoichiometrically needed for
complete combustion of the hydrocarbons.
[0046] In a preferred embodiment of the invention, the gases
produced by burner 12 exit reactor 10 through pipe 26 and are
quenched down to a temperature below about 300.degree. C. by
contact with cooling water 28 from a suitable source 29 in quench
orifice 30. Cooled gases and water then optionally pass through
heat exchanger 32 where steam is produced from water 34 from source
36, and fed to burner 12 through pipes 20 and 21. The reducing gas
38 is then treated in a scrubber 40 where it contacts water 42 from
source 44. Hydrochloric acid formed by combination of chlorine
atoms of the polychlorinated biphenyls with hydrogen produced by
the partial combustion of the hydrocarbons, is absorbed by water
and is extracted in solution with water 48. This acid water may be
further treated for concentrating the hydrochloride acid for sale
or may be treated with sodium hydroxide for neutralization
thereof.
[0047] The reducing gas 46 produced from the contaminated
hydrocarbons may be utilized as synthesis gas, as a chemical
reactant in other chemical processes or as a fuel for steam or
power production.
[0048] Liquid hydrocarbons contaminated with PCB's are mainly
contained in electrical equipment, e.g. transformers, capacitors
and the like, at a variety of concentrations. Concentration of
PCB's in the refrigerating oils of electrical equipment may be
below 50 ppm (parts per million) up to almost pure PCB's. One of
the main properties of PCB's is their chemical stability and
therefore they do not react easily with oxygen due to the strong
chlorine chemical bonds in the molecule and their low calorific
value. Materials with high concentrations of PCB's may not sustain
a stable reaction with oxygen, and therefore it is recommended to
mix them with other non-contaminated hydrocarbons, thus lowering
the concentration to levels below about 600,000 ppm (60% by
weight), and preferably below about 300,000 ppm and more preferably
below about 110,000 ppm.
[0049] Referring again to FIG. 1, contaminated hydrocarbons are
transferred from holding tank 50 through pipe 52 provided with
valve 54 to mixing tank 56. Mixing tank 56 is provided with
stirring means 58 to provide for a homogeneous composition of the
materials fed to reactor 10, and with load cells 60. Hydrocarbons
contaminated with PCB's are transferred from holding tank 62
through pipe 64 provided with valve 66 to mixing tank 56. Signals
from load cells 60 are used by controller 68 for preparing batches
of hydrocarbons with predetermined levels of concentration of
PCB's. After mixing, hydrocarbons are passed to feed tank 70
through pipe 72 provided with valve 74. From feed tank 70
hydrocarbons are fed to burner 12 by any one of pumps 76 or 78
through pipe 16 provided with control valve 80.
[0050] The proportions of steam, oxygen and hydrocarbons are
controlled by controller 68 and control valves 19, 21 and 80,
according to predetermined values of process parameters comprising
the desired minimum temperature and residence time in the reaction
chamber 24 to destroy the PCB molecules, resulting in up to and
including full destruction of the toxic materials. The temperature
for destruction of PCB's at the outlet of reactor 10 is in the
range from about 1000.degree. C. to about 1100.degree. C. Flame
temperatures may reach more than 2000.degree. C., but the average
temperature of the gases after endothermic reactions take place to
produce the reducing gas--with a typical composition of about 45.6%
hydrogen; about 34.6% carbon monoxide; about 18.9% carbon dioxide;
about 0.6% methane; about 0.4% nitrogen; and traces of other
materials--lower the gases temperature to about 1000.degree. C.
This gases temperature may be regulated by the proportion of steam
to oxygen and hydrocarbons. The reducing character of the gases
within reactor 10 prevents dioxins and furans from forming, thereby
assuring a safe operation of the PCB's destruction process, in
contrast with the incineration processes where an excess of oxygen
propitiates such formation unless the hot gases are immediately and
rapidly quenched.
[0051] The invention also comprises a burner or injection lance to
produce a coherent flame with the mixture of contaminated
hydrocarbons, steam and oxygen and feed this mixture into the
high-temperature reaction chamber 24 of reactor 10. Any burner that
provides for atomization of liquids so that hydrocarbons are not
cracked by the high temperature of the reaction chamber forming
soot and lowering the gasification efficiency can be used. In a
preferred embodiment, a tube-in-tube burner is used to produce a
long coherent flame favoring full contact and mixture of the
reactants.
[0052] Referring to FIG. 2, a burner 110 for the partial combustion
of hydrocarbons, useful for securing destruction of toxic
compounds, is provided with a first inlet 112 and second inlet 114
and outlet 116. The burner is also provided with flange means 128
for fixing to reactor 10 as well known in the art. Liquid
hydrocarbon is fed through first conduit 118 to said first inlet
112 and then is injected through inner pipe 120 into outer pipe
110. A mixture of steam and a free-oxygen-containing gas is fed
through second conduit 122 to second inlet 114 and flows along with
liquid hydrocarbon through outer pipe 110.
[0053] By having a ratio of length 124 to diameter 126 of the
burner pipe 110 greater than or equal to 4, preferably in the range
of about 30 to about 36, the liquid hydrocarbon and the gaseous
mixture of steam and oxygen develop a flow pattern known as
dispersed flow, e.g. a mixture of small liquid droplets entrained
by the gas. This intimate contact of reactants minimizes soot
formation and increases the efficiency of the gasification process.
For such dispersed flow pattern to develop velocity of the gaseous
phase is one important consideration, therefore, the inner diameter
of pipe 110 is selected according to the rate of hydrocarbon feed
so that the actual average velocity of the gas is from about 40 m/s
to about 60 m/s, preferably from about 45 m/s to about 55 m/s.
[0054] Typically 1 NCM of steam/oxygen gas required for 1 kg of
hydrocarbon. Once the flow rate of reactants is defined, the inner
diameter and length of pipe 110 are selected.
[0055] The burner-lance of the present invention for performing the
partial combustion of the hydrocarbons provides an intimate contact
of the liquid and gaseous phases through a pipe in contrast to the
structures of burners of the prior art which rely on directing the
stream of gas so that it impinges in a separate stream of liquid.
The burner of the invention produces a compact coherent flame with
a high reaction efficiency because the velocity vector of the
mixture is sufficient to project it freely into the reaction
chamber, much like a long rifle cannon directs a bullet. The prior
art, by contrast, directs separate streams of liquid and gas in
several directions at the tip of the burner in order to promote
impingement thereof one upon the other and dispersing the particles
in the reaction space.
[0056] It has been found that the burner of the present invention
may also be utilized for gasification of hydrocarbons other than
oils contaminated with PCB's. For example, the invention may also
be applied for gasification of a slurry of ground solid
hydrocarbon, for example pet-coke or coal and for destruction of
other type of toxic materials, for example, insecticides, Freon
gases, solvents, chloroflurocarbons, biocides and hospital
wastes.
[0057] The present invention is additionally described by way of
the following illustrative, non-limiting Examples that provide a
better understanding of the present invention and of its many
advantages.
EXAMPLES
[0058] The following examples are set forth to illustrate various
embodiments in accordance with the present invention. The following
examples, however, are in no way meant to limit the present
invention.
Example 1
[0059] A burner of {fraction (3/4)} inches inner diameter was used
for gasifying three different types of liquid hydrocarbons without
toxic materials and producing a useful reducing gas as follows:
1 Flow rate Unit Run 1 Run 2 Run3 Hydrocarbon: (Kg/Hr) 54.0 56.3
52.0 Oxygen: (NCM/Hr) 54.0 34.4 47.2 Steam: (NCM/Hr) 35.0 32.7
37.0
[0060] The hydrocarbons were treated according to the invention
producing a reducing gas in the amount and composition (dry basis)
shown below:
2 Reducing gas: (NCM/Hr) 142.0 104.0 143.2 H2: % vol. 47.90 45.7
46.8 CO: % vol. 30.23 24.1 27.0 CO.sub.2: % vol. 18.79 24.5 19.9
CH.sub.4: % vol. 2.61 5.3 6.0 N.sub.2: % vol. 0.47 0.4 0.2
Example 2
[0061] Oil contaminated with PCB's was destroyed according to the
invention in two runs, one at a PCB concentration of 5% by weight
(50,000 ppm) and the other at a PCB concentration of 10% by weight
(100,000 ppm).
[0062] The values of process parameters were as follows:
3 Unit Run 1 Run 2 Run 3 Concentration of PCB's 0% 5% 10%
Hydrocarbon: (Kg/Hr) 56.9 58.2 60.6 Oxygen: (NCM/Hr) 62.8 61.5 62.8
Steam: (NCM/Hr) 74.8 73.4 77.0 Temperature: .degree. C. 1241 1268
1298 Pressure: Kg/cm2 gage 3 3 3
[0063] The hydrocarbons were treated according to the invention
producing a reducing gas in the amount and composition on a dry
basis shown below:
4 Reducing gas: (NCM/Hr) 142.6 134.8 132.2 H.sub.2: % vol. 46.65
46.09 45.60 CO: % vol. 33.44 34.19 34.56 CO.sub.2: % vol. 18.71
18.54 18.86 CH.sub.4: % vol. 0.97 0.92 0.62 N.sub.2: % vol. 0.23
0.26 0.36 Nitrogen Oxides: mg/m3 2.5 2.9 4.2 SO.sub.2 mg/m3 7.5 8.7
4.4 HCl: mg/m3 <0.58 <0.57 <0.29 Total PCB's mg/m3 2.23E-0
53.4E-05 8.97E-04 Dioxins and Furanes ng-EQT/m3 6.5E-06 8.1E-06
7.1E-06
[0064] Values of some process parameters were:
5 Temperature: .degree. C. 1241 1268 1298 Pressure: Kg/cm2 gage 3 3
3
[0065] The extremely low values of PCB 's in the product gases show
that the invention is very efficient in the destruction of PCB's
and that the reducing atmosphere created by the partial combustion
and the intimate mixing of the reactants do not favor formation of
dioxins and furanes.
[0066] The cooling water employed for cooling and washing the
reducing gases in cooler 40 was analyzed giving the following
results:
6 Concentration of PCB's 0% 5% 10% Chlorides in make-up water: mg/l
58 Chlorides at cooler inlet mg/l 66 651 1864 Chlorides at cooler
outlet mg/l 74 756 1850 PCB's at cooler outlet mg/l <0.002
<0.002 <0.002 Dioxins + Furanes ng/l 9.4E-05 1.5E-04 8.4E-03
cooler outlet
[0067] Comparison of efficiency and emission levels of the process
of the invention with the levels of contaminants permitted
according to U.S. Regulations:
7 Parameter Unit 0% 5% 10% U.S. Reg Efficiency PCB % -- 99.9999998
99.99999972 99.9999 destruction (min) Dioxins and Furanes ngEqt/m3
6.505E-06 8.100E-06 7.072E-06 0.5 Suspended particles mg/m3 6.3 2.1
2.7 30 SO.sub.2 mg/m3 5.04 5.81 2.93 80 Nitrogen Oxides mg/m3 1.67
1.94 2.81 300 Hydrogen chloride mg/m3 <0.039 <0.038 <0.019
15
[0068] Various modifications and variations of the described
compositions, materials and methods of the invention will be
apparent to those skilled in the art without departing from the
scope and spirit of the invention. Although the invention has been
described in connection with specific preferred embodiments, it
should be understood that the invention as claimed should not be
unduly limited to such specific embodiments. Indeed, various
modifications of the described modes for carrying out the invention
which are obvious to those skilled in the art or in related fields
are intended to be within the scope of the following claims.
* * * * *